I live just west of Minneapolis, and I grow hardneck garlic types. They are the ones best adapted to northern climates, and better tasting with more complex flavoring, too. As for myself, I prefer the varieties that aren't so hot, as they allow the other flavors to shine more. Hardneck garlic generally has larger cloves but fewer per bulb, which make them easier to peel. I used to grow hundreds of bulbs each year and give them away to friends and neighbors, until the growing space was usurped by "more important" gardening endeavors. Now, even 5 years later, they still tell me how wonderful those yearly gifts were, and how dearly they are missed.
I had always planted the last week of September, and sometimes I would have significant emergence before winter, but it didn't seem to hurt them. But now, with the climate changing, our falls are consistently longer, and I now plant the first or second week of October.